Microstructure characteristics, dynamic kinetics and thermal properties of Mg77+xNi20-xCe3 (x=0, 5, 10, 15) hydrogen storage alloys.

Utilizing element substitution to enhance the hydrogen storage capabilities of Mg-based alloys represents a promising approach in the quest for efficient energy storage solutions. Thereby, in this paper, Ni is chosen to substitute a portion of Mg in a Ce–Mg-based alloy aimed at improving its hydriding and dehydriding performance. Mg 77+ x Ni 20- x Ce 3 (x = 0, 5, 10, 15) alloys are successfully prepared by the vacuum induction melting method. The structural characterizations of the alloys are performed using X-ray diffraction and scanning electron microscope. The alloys are composed of a primary phase of Mg 2 Ni, lamella eutectic composites of Mg + Mg 2 Ni, and some amount of CeMg 12 and Ce 2 Mg 17. In the as-cast Mg 87 Ni 10 Ce 3 alloy, the Mg 2 Ni phase disappears, transforming into a typical eutectic structure of hundreds of nanometers thick Mg–Mg 2 Ni lamellas. This structure significantly enhances the hydrogen storage kinetics, with a hydrogen absorption capacity of 5.66 wt% at 653 K and a desorption capacity of 5.45 wt% over 2 h at 683 K, outperforming other alloys. Moreover, its peak hydrogen release temperature is significantly lower than that of the Mg 92 Ni 5 Ce 3 alloy. The formation of the CeH 2.29 phase within the alloy acts as a catalyst, effectively improving the exothermic and endothermic kinetics of hydrogen absorption and desorption, resulting in a much lower hydrogen desorption activation energy compared to MgH 2. However, the variation in the activation energy of the alloy remains limited, ranging between 66.6 ∼71.1 kJ/mol. [Display omitted] • Mg 77+ x Ni 20- x Ce 3 (x = 0, 5, 10, 15) alloys were prepared in an induction furnace. • Ni substituting for Mg significantly lowers the peak temperature of hydrogen release. • Ni substituting for Mg reduces the desorption activation energy values. • The Mg 87 Ni 10 Ce 3 alloy can absorb more than 5.66 wt % H 2 within 120 min at 653K. [ABSTRACT FROM AUTHOR]